The present invention relates to a rotary wing aircraft with rotor blades mounted on a rotor head and with jet drive.
Rotary wing aircraft or helicopters are known in which the rotor is driven by an engine, for instance an aircraft engine or a gas turbine.
Such helicopters require a torque compensation around the yaw axis which can be achieved either by the arrangement in pairs of identical rotors with opposite direction of rotation or by a tail rotor. The structural expense and the loss in power by transmissions and the like are considerable.
On the other hand, helicopters with reaction drive do not require torque equalization since there is no drive moment on the fuselage of the aircraft. To be sure, also in the case of helicopters of this type, the measures necessary for the drive are considerable in lieu thereof; this is because the rotors require drive units at their blade tips, or gas turbines arranged in the fuselage of the aircraft, for supplying hot gas to thrust nozzles arranged on the blade engine.
An object of the invention is to create a rotary wing aircraft of the aforementioned type, the drive of which for the rotor blades requires the least possible expense without requiring torque compensation around the yaw axis in order to have available an aircraft which can lift large loads with small engine power, which can be purchased and maintained at low cost, and which are simple to handle and are of low weight.
In accordance with the invention, this foregoing object is achieved in the case of a rotary wing aircraft of the above-indicated type in the manner that the rotor blades mounted on the rotor head are hollow and have at least one outlet opening on their trailing edge for the compressed air fed via the rotor head.
The compressed air can be produced in this case by a compressor which is arranged in the fuselage of the rotary wing aircraft and forces compressed air, via the hollow rotor head, into the rotor blades. The outlet openings on the trailing edge of the rotor blades can be developed as holes or slots which are distributed over a part of the blade length or over the entire length of the blade.
In one particularly advantageous embodiment of the invention, the rotor head is developed as an air suction connection in which there is mounted a suction member, the pressure side of which is connected to the hollow rotor blades.
The invention provides a helicopter having a novel rotor system in which air is drawn from above--or below--and forced into the hollow rotor blades, where it produces at the outlet slots the desired reaction drive for the rotor and, in addition, results in a lengthening of the blade profile so that the emerging air at the same time produces the rotary drive and increases the lift. The centrifugal acceleration of the compressed air in the hollow rotor blades increases the reaction effect.
In a further form of the invention, the suction member is an impeller (i.e. casing screw of a compressor) which is rotatively driven around the axis of the rotor head and behind which stationary guide vanes are arranged in the suction direction. Instead of the impeller, a propeller or a prop fan can also be provided. The guide vanes have the job of reducing the rotation of the air to a minimum.
For the rotary drive of the suction member an engine is provided which constitutes an internal combustion engine and can be fastened in the non-rotatable rotor head itself. In this way, a very compact construction is obtained, the fixed rotor head requiring no torque compensation, so that no measures are necessary for a tail rotor or the like. The sole rotating member in the rotor is the suction member, which does not require torque equalization. For this there suffices a simple rudder which can be pivoted oblique or combined on the tail of the rotary wing aircraft and be blown against from top to bottom by the rotor so that the desired rotation around the yaw axis can be carried out in a hovering condition.
Instead of the rudder, control nozzles can also be developed on both sides of the tail, they being connected by connecting lines to the pressure side of the rotor head.
It is particularly advantageous if the engine for the drive of the suction member is seated in the communication path between its pressure side and the hollow rotor blades. In this way the air drawn in serves to cool and at the same time to charge the engine, which thus does not require any compressor. The exhaust gases of the engine, on their part, produce additional pressure in the rotor blades, thus increasing the torque; furthermore, they heat the rotor blades thereby preventing icing. Since the exhaust gases are not given off directly outward but flow into the rotor blades, the latter act to dampen noise, as a result of which the sound level of the helicopter is very low. The suction opening which is developed on the top of the rotor head also produces a reducing effect on the noise level since the sound here is lost in funnel shape in upward direction.
It should be pointed out here that the vacuum produced by the suction member exerts an additional lifting force on the aircraft.
As a further development of the invention, the rotor head is developed behind the pressure side of the suction member as a radially outwardly opening annular space on the cylindrically developed open outer surface of which there is mounted a radially inwardly open connecting ring which is rotatable around the axis of the rotor head and bears the rotor blades in the region of radial outlet openings.
Since in this arrangement the connecting ring is mounted for free rotation on the rotor head, no devices such as a freewheel or coupling are necessary in order to place the rotor in autorotation when the drive fails. The rotor blades themselves are arranged on the connecting ring via flapping hinges or drag hinges. The angle of attack of the rotor blades can be kept very small, for instance 4.degree., resulting in the structural advantage that switching to autogyro operation is dispensed with.
The displacement of the rotor blades around the drag hinge can be effected in very simple fashion since suitable devices can be arranged on the fixed rotor head, for instance a swashplate or a cam control.
In order to swing the rotor plane so as to produce a tractive force for forward movement it is possible to fasten the rotor head adjustably via a hinge bearing on the rotary wing aircraft. In the event of such a measure, the means for the blade displacement around the drag hinge are dispensed with.
In addition, the rotor head can be fastened displaceably on the rotary wing aircraft in the longitudinal direction thereof so that trimming of the center of load can be effected.
In accordance with another feature of the invention, deflector ribs leading to the outlet slots are fastened in each rotor blade. Their length preferably increases toward the tip of the rotor blade. In this way, part of the stream of air flowing through the rotor blade is deflected at each deflection rib to the corresponding outlet slot, while a further part passes to the outlet slots provided further to the rear.